Sustainable Land Use and Watershed Management in Response to Climate Change Impacts: Case Study in Srepok Watershed, Central Highland of Vietnam

Introduction

Soil and water resources in many countries are currently under severe pressure due to human intervention and changing runoff patterns caused by climate and land use changes. Population growth and human-induced development have accelerated the speed of land use/cover changes that in turn affect hydrological processes. In addition, climate change may affect many aspects of the natural ecosystems. Hence, understanding climate change impacts on hydrological conditions is essential to enable more efficient soil and water resource development.

The Srepok river basin, a sub-basin in the Lower Mekong river basin was selected as the study area (Figure 1). At present, there are many critical issues for soil and water resource management in this basin (The Government of Vietnam, 2006). These problems range from:

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  Hydrological variability (including floods and droughts) to environmental degradation (including pollution of waterways and deforestation of catchments),

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  Erosion and resultant sedimentation of reservoirs,

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  Over-exploitation of groundwater,

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  Conflicts over the use of water for different purposes, and

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  Trans-boundary conflicts (inter-provincial and inter-district).

Figure 1.

Srepok watershed in Central Highland of Vietnam

The Vietnamese provinces that share the Srepok catchment are undergoing rapid and intensive development, much of it based on agriculture. For example, Dak Lak province supplies 50% of the country’s coffee production. Likewise, hydropower development in the Srepok river basin has been rapid. There are currently five dams on the basin, with two more proposed. The operation of these hydropower stations will cause numerous complications downstream of the Srepok river basin, especially as there is likely to be a significant change in the flow regime. This may change the water availability for downstream users, as well as affect the river ecology and accelerate erosion of the riverbank. In addition, there are large numbers of irrigation and water supply reservoirs throughout the catchment, as well as significant (although depleted) groundwater reserves. Moreover, changes to stream flow and abstraction in Vietnam is of great relevance to downstream Cambodia. In the 1980’s and 90’s, significant changes of land use occurred in the basin due to dramatically increasing world coffee prices (The Government of Vietnam, 2006). Notably, the area under coffee cultivation increased to more than 200,000 hectares, compared with the previous few tens of thousands of hectares. This huge increase resulted in the mass exploitation of groundwater without any planning or regulation, since many small-sized reservoirs were constructed to provide surface water for the irrigation of coffee. These actions led to the deterioration and depletion of ground and surface water resources. Consequently, droughts and the scarcity of water exacerbated during the basin’s dry seasons.

Therefore, to make suitable adaptation plans for soil and water resources use in this basin, decision makers need to understand the extent of the potential impact of both climate change and human activity on local soil and water resources. So far, a few studies have quantified the combined potential future impacts of climate and land use change on hydrology in the Srepok watershed (Kawasaki et al., 1010; Ty et al., 2012; Khoi, 2013) but there has been no study done on assessing the impact of climate and land use change on sediment yield in the basin.

The overall objective of this research was to investigate changes in stream flow, sediment load, and hydrological processes resulting from land use change and climatic variation in the Srepok watershed, which is located in the Dak Lak and Dak Nong provinces, Vietnam. The specific objectives were as follows: